1. Field of the Invention
The invention relates to devices for firing projectiles and more particularly to such devices utilizing a fluid propellant.
2. Prior Art
Conventional projectile firing weapon systems utilize a measured amount of solid propellant confined in a shell or cartridge casing capped by the projectile and are fired by a percussion cap or primer. The casings, which are normally brass, make such ammunition expensive and heavy to carry and therefore a good deal of effort has been expended lately on developing caseless ammunition in which the solid propellant is attached directly to the projectile without a casing. This arrangement has its own special problems, such as the development of a propellant which is resistant to chipping and cracking when used in automatic weapons and under normal field conditions. Some of these weapons utilize the heat generated by rapid compression of air to ignite the solid propellant while others rely upon impact ignition.
Several types of fluid operated weapons which inherently eliminate the need for a casing have also been proposed. In some, such as those disclosed in U.S. Pat. Nos. 1,383,111 and 3,728,937, a spark or glow plug ignites the fluid propellant. In U.S. Pat. No. 2,947,221 compression ignition of the liquid propellant is utilized to fire the weapon. These prior art weapons for the most part rely upon mechanical devices for charging the fluid propellant into the firing chamber. In U.S. Pat. No. 3,728,937, the operator manually strikes one button to admit butane and another to admit oxygen to the firing chamber after the projectile has been inserted and the bolt closed manually. In U.S. Pat. No. 1,383,111 a pump action is used to charge the firing chamber and in U.S. Pat. No. 3,800,657 the liquid propellant is charged into the firing chamber from dosing chambers by pistons. U.S. Pat. No. 3,255,669 suggests that a gaseous propellant be confined in a detonation chamber which is separated from the barrel and the projectile by a valve until the trigger is pulled and the gas is ignited in order to maintain the gas pressure.
Automatic weapons in which a portion of the gases which drive the bullet down the barrel are vented back to cycle the bolt and reload another cartridge from a magazine are well known. These weapons often provide a semi-automatic mode in which the trigger must be released and resqueezed to fire the next cartridge and a fully automatic mode in which cartridges are loaded and fired continuously as long as the trigger is squeezed. Weapons of this sort are available for both cased and caseless ammunition. While most of these weapons have a fixed rate of fire, it has been suggested that the rate of fire may be varied by adjusting the bleed rate of a pneumatic cylinder connected in the mechanical mechanism.
It is an object of the present invention to provide an improved projectile firing device using a fluid propellant which is simple in design, easily constructed and serviced and is dependable. It is also an object of this invention to provide such a device which is capable of automatic or semi-automatic operation and in which the muzzle velocity and rate of fire are adjustable. Other objects of the invention will be apparent from a reading of the detailed description of a preferred embodiment which follows.